1. Field of the Invention
This invention relates to a device and process for increasing analyte concentration in a sorbent from a source of analytes contained in a sample by increasing a temperature differential between said sample and said sorbent.
2. Description of the Prior Art
As described in International Application Number PCT/CA91/00108 filed on Apr. 2nd, 1991 by Janusz B. Pawliszyn entitled Method and Device for Solid Phase Microextraction and Desorption, it is known to extract analytes using a fiber (either uncoated or coated with a polymeric coating) to extract organic compounds from their matrix and to directly transfer the analytes to an analytical instrument through thermal desorption. For example, the analytes can be transferred into a gas chromatograph through thermal desorption in a GC injector. The fiber can extract the analytes by dipping all or part of the fiber directly into the sample containing analytes or by contacting the fiber with a headspace located above the liquid containing analytes. This process is referred to as solid phase microextraction (hereinafter "SPME"). SPME has been used successfully for analyzing volatile organic compounds (those listed in U.S. Environmental Protection Agency Method 624, polyaromatic hydrocarbons (PAH's), polychlorinated biphenyls, phenol and its derivatives in aqueous samples. SPME can also be used to analyze volatile and semi-volatile organic compounds in more complex samples such as soil and sludge by having the analytes contact the fiber in a headspace above the sample matrix. Sometimes, the SPME approach suffers from disadvantages in that many matrices do not release sufficient analytes. Thus, the analytes transferred to the fiber are not sufficient to produce a detectable signal when the analytes are desorbed in an analytical instrument. Also, the SPME is typically not a quantitative extraction method and therefore, it requires careful calibration procedures.